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Daily check the water level in the field to see that it is not rising or falling unusually quickly. If this occurs, find out what is causing it. Any leaks should be clogged. A shovel or hoe should be carried on these visits.
Some farmers throw a little feed every day in order to monitor their fish stocks.
In intensive systems, early morning checks to see if fish are gaping are advisable.
Feeding and fertilizing should normally help fish grow. However, it is not a major consideration in lightly stocked fields (below 3 000/ha), where fish should be able to forage sufficiently for themselves.
Families who would like to stock more heavily (and therefore to feed and fertilize) need to consider the following:
a. Will they have time to feed or fertilize well? (How far away is the field from their house? What other work do they have to do?)
b. Can they get feed or fertilizer? Is it easily available in the area? Is it affordable?
It is difficult to draw a line between «feed» and «fertilizer» especially since manure can be used as both. Inorganic fertilizers can be used. So can any nontoxic organic material.
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Manure is often the most important addition, by weight. Either fresh or dried manure can be used. A little caution with fresh manure may be needed if water is stagnant, but it has been observed that up to 300 kg/ha/week go into such systems without causing harm. Replenishing manure as the fish consume it is another way to cope.
Rice bran is commonly used as a fish feed. It works well in nurseries, but is usually not needed in extensive rice-fish culture. If farmers have to pay for it, they probably should not use much, once fish have entered the field.
Some farmers use rice hulls in their systems and some fish species eat these eagerly. Most of the hull is not digested, but gets spread around the field by the fish.
Kitchen wastes and leftovers of any kind can also be given.
Different kinds of water plants work well: Azolla, Wolffia, duckweed (Lemna), pak boong or kangkong (Ipomoea aquatica) and water mimosa are examples. Different fish species will have different preferences but silver barb will eat any of these.
Crop by-products are also acceptable: cabbage leaves and corn cobs have been used by some farmers. Cassava leaves are also popular. Since some cassava varieties may be poisonous, it is advisable to dry cassava leaves before feeding them to fish.
Termites are a very nutritious feed and are especially helpful in nurseries. Nests are chipped over the pond or field and the termites fall into the water, where they are rapidly consumed. Termites are usually not needed once fish have entered the ricefield; if farmers continue to use them heavily throughout the season, they may run out of nests! Other insects, shrimps and worms are similarly nutritious.
Caution: Termites have been reported to cause fish mortality if fed live as these are swallowed whole. The termites continue to bite with their large jaws while in the stomach, causing fatal injuries and perforations to the stomach wall. A safe way to utilize this excellent food source is to drown the termites in a separate pan or bucket before feeding them to the fish. |
Rice straw is not usually eaten directly by fish, but feeds small plants and animals on which fish feed. It can be used anywhere, but may be especially helpful in turbid nursery ponds.
Any otherwise unused dead animals, entrails or body parts can be put to use. In ricefields, they can go directly into the water for fish consumption. In nursery ponds, large, decaying animals can contaminate the pond. Some farmers suspend animal parts over the pond. These attract flies, which lay eggs on the meat; maggots can then be knocked off the meat into the water to feed the fish.
Jute or kenaf retting can make water temporarily unsuitable for fish culture. This is a process in which the freshly cut plant stems are submerged in ponds and ditches to let the soft plant material rot off, with the desired fibers remaining, which are dried and processed. In these ponds, the water turns black, oxygen levels drop to near zero and the water smells bad. The retting is very effective, however, in clearing up turbid water. After the retting is finished, pond water quality is often improved. Also, small amounts of jute or kenaf will not harm fish and the rotting material provides feed. Larger amounts can be placed in stagnant water. Good figures for safe rates for fish, unfortunately, are not available, so only small amounts should be used and the fish should be checked every morning to see if they are gaping.
Other examples of feeds include mulberry leaves, banana leaves, bat or livestock dung, animal feed leftovers, coconut oil residues and Leucaena leaves. No list of potential feed stuffs will be complete.
In densely stocked fields (over 5 000/ha), continuous feeding and fertilizing become important, particularly as the fish grow. Giving small amounts of feed a couple of times a day may be advisable. Check to see how quickly a known amount of vegetation or manure gets consumed. If some amount remains after an hour, there is no need to increase the rate. If it disappears within half an hour, increasing the amount is advisable.
Issues for further consideration The example relates to very extensive rice-fish growout systems with low stocking rates as implemented in northeast Thailand, which do not require feeds and fertilizers. On the other hand, more intensive rice-fish systems for nursing or food fish as they exist elsewhere in Thailand and other countries have higher stocking densities, frequent water exchange and, most importantly, specific feeding and fertilizing methods. |
